In optical fiber manufacturing processes, fiber is drawn from a large-diameter glass structure known as a preform. The fiber is drawn through a generally vertical structure known as a draw tower. A furnace or torch may heat a portion of the preform at the top of the draw tower. Molten glass from the preform extends downwardly, forming into a fiber shape. The fiber may pass through a chiller tube filled with inert gas such as helium. The fiber cools and solidifies as it proceeds through the draw tower. Generally, the higher the speed at which the fiber is drawn, the taller the tower needs to be to sufficiently cool the fiber. One challenge in improving fiber production systems and methods is how to increase the rate of fiber production, i.e., throughput, without increasing the height of the draw tower, which may be several stories in height.
One or more coatings may be applied to the fiber in the draw tower. For example, the draw tower may include a primary coating applicator, followed by (i.e., beneath the primary coating application) a secondary coating applicator. One or more curing lamps that produce ultraviolet (UV) light may follow the coating applicators. The effectiveness of UV curing may depend on various factors, including temperature; UV curing of the primary coating is more effective when the coated fiber is cooler. The curing lamps may be, for example, broad-spectrum mercury arc lamps. In some draw towers, there may be no curing lamps between the primary and secondary coating applicators. That is, to help minimize the height of the draw tower and/or maximize draw speed, the secondary coating may be applied over the primary coating (in a “wet-on-wet” manner), and then both the primary and secondary coatings may be cured simultaneously. Curing of the primary or inner coating may be hampered by opacity of the secondary or outer coating, which is commonly tinted with a color. Higher-speed operation may exacerbate the challenge of fully curing the primary coating before the fiber exits the bottom of the draw tower.